Unraveling the role of single layer graphene as overlayer on hematite photoanodes

Author(s)

Carminati, Saulo Amaral ^[1] ; Barbosa, Andre do Nascimento ^[2] ; Martins de Freitas, Andre Luiz ^[3] ; Freire, Jr., Fernando Lazaro ^[2] ; Souza, Flavio Leandro ^[3] ; Nogueira, Ana Flavia ^[1]

Affiliation

^[1] Univ Estadual Campinas, Lab Nanotecnol & Energia Solar, Inst Chem, POB 6154, BR-13083970 Campinas, SP - Brazil

^[2] Pontifical Catholic Univ Rio de Janeiro PUC Rio, Dept Phys, Rio De Janeiro - Brazil

^[3] Fed Univ ABC UFABC, CCNH, Santo Andre - Brazil

• Document type: Journal article
• Source: JOURNAL OF CATALYSIS; v. 372, p. 109-118, APR 2019.
• Web of Science Citations: 0

Abstract

In this work, the role of the single layer graphene as overlayer on hematite photoanodes surface was investigated for water oxidation reaction via photoelectrochemical process. Single layer graphene (SLG) was synthesized by chemical vapour deposition (CVD) and transferred from the copper foil to the alpha-Fe2O3 photoanode surface. To ensure the purity and quality of SLG, elemental composition of the samples was investigated in all steps and no metal (Cu) trace was found after the transference onto the photoanode surface. The photocurrent density of alpha-Fe2O3/graphene photoanode was increased from 1.25 to 1.64 mA cm(-2) at 1.23 V-RHE in comparison to bare alpha-Fe2O3 photoanode. The role of SLG added on alpha-Fe2O3 and the charge carrier dynamics were investigated combining transient absorption spectroscopy (TAS) and surface photovoltage spectroscopy (SPS). These combined techniques revealed that the photogenerated holes had their lifetime increased as a function of applied bias and after the SLG deposition onto the alpha-Fe2O3 photoanode surface. As consequence, the photochemical separation and transfer of the photogenerated charge carriers became more efficient in the presence of SLG. The incorporation of SLG on alpha-Fe2O3 photoanode is believed to suppress the surface traps, enabling holes to diffuse into the solid-liquid interface and promoting water oxidation reaction driven by sunlight irradiation. (C) 2019 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 15/23775-3 - Metal oxides nanocomposites with reduced graphene oxide for water splitting reactions and photocatalytic reduction of CO2
• Grantee: Saulo Do Amaral Carminati
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/11986-5 - Research Division 1 - dense energy carriers
• Grantee: Ana Flávia Nogueira
• Support type: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 14/11736-0 - Development of inorganic material nanostructures for conversion and storage of solar energy
• Grantee: André Luiz Martins de Freitas
• Support type: Scholarships in Brazil - Doctorate (Direct)